oil pressure is running on the low side on factory oil pressure gauge, a shop installed a second one separately, they tapped in right about the oil filter housing. the gauge has been running on the low side about 25, now has totally dropped off. Is there a better place to tap into, or is there build up cause the gauge to be off.

Maybe your pressure is that low. I would remove the factory sender and check the pressure with a known good gauge.

I run my aftermarket oil pressure sender off the oil filter housing, can't get much better than that, 25psi warm idle is normal on all my 12valves, I'd get uneasy lower than that. Maybe a leaky seal on turbo? Tired engine? Probably a number of things it could be.

-j

Check your oil pressure with a good quality MECHANICAL gauge. I have little faith in a electrical oil pressure gauge. FWIW, it is not uncommon for the factory gauge to be way off.